Development of plant and tooling technology with process data analysis for the pultrusion of sustainable, recyclable lightweight structures.

Project Overview

In the CaproPULL project, a manufacturing process with associated plant and tooling technology, as well as powerful process data analysis, is being developed for the production of continuously reinforced thermoplastic profiles. The profiles produced in this way are intended to be of higher quality and recyclable compared to the state of the art. They thus tap into the potential to produce energy- and resource-saving components for many applications. The consortium consists of Bauer Systeme GmbH for plant technology, Alfred Härer GmbH for tooling technology, Selfbits GmbH for production data acquisition, and the Fraunhofer Institute for Chemical Technology ICT for process development and project management.

Project Duration

November 2021 – October 2023

Funded by


Circular economy and resource efficiency, alongside costs, are the key drivers for the competitiveness of new products. To reduce environmentally harmful emissions, new materials and processes are necessary to save component weight and enable closed-loop circulation. Powerful continuously reinforced plastics with a thermoplastic matrix made of polyamide 6 have great potential for solving these challenges. A novel process for producing such high-performance composites is “in-situ pultrusion” (pultrusion = continuous pulling process) with the monomer ε-caprolactam. The low-viscosity monomer ε-caprolactam offers decisive advantages over comparable matrix systems and polymerizes during processing into polyamide 6. Thus, this continuous process allows cost-effective and highly productive production of high-performance profiles based on a recyclable thermoplastic material.

Project Objective & Approach

The goal of the research project CaproPULL is to develop suitable sensor-based plant and tooling technology with process data analysis for the in-situ pultrusion process, enabling the reliable processing of the ε-caprolactam monomer. This will allow thermoplastic continuous fiber-reinforced profiles to be manufactured robustly and reliably, which are at least equivalent to the current state-of-the-art thermoset profiles in terms of quality and properties. The addition of recyclability to these profiles and the expected cost-effectiveness of the new material and process are expected to provide a significant competitive advantage over the current state of the art. Pultruded profiles have a wide range of applications, including in the automotive industry, as support systems for renewable energies, in the construction sector, and even in the chemical industry. With the support of associated partners, the project results are intended to be transferred to these industries as well.


The innovation in the project primarily lies in the reliable processing and the associated requirements. Due to the low, water-like viscosity of ε-caprolactam and the imperative avoidance of moisture contact during processing, challenges arise regarding the processing plant, tooling technology, and data utilization. The innovation of the project lies in achieving a stable and mass-production-capable process. The pultrusion process is supported by data acquisition, management, and utilization, facilitating integration into the digitized production of the future and ensuring improvement and traceability of the quality of the profiles produced.

The contribution of Selfbits to the project

The Selfbits GmbH provides tailored MES solutions along the entire value chain, collecting real-time data on the current state of products and production resources. By utilizing real-time data, product quality can be enhanced, and production lead times can be reduced. Thus, Selfbits brings comprehensive expertise in data acquisition, processing, and analysis to the project. In the CaproPULL research project, Selfbits GmbH is responsible for capturing production data and processing it using suitable analysis algorithms.

Through data-based control and analysis, manufacturing processes can be precisely analyzed, optimization potentials can be uncovered, and productivity improvements can be realized in line with continuous improvement processes. These competencies are particularly crucial for in-situ pultrusion, as the quality of the produced profiles can vary due to changing environmental conditions. Data-based process control with corresponding recommendations aims to ensure quality requirements for the profiles.

In the first step, the development of a digitized parameter acquisition for the continuous production of sustainable profile structures will be designed to be flexible enough to integrate the various components of the production line adaptively and standardized regarding data acquisition in a central data acquisition system. The individual components include:

  • The pultrusion plant itself,
  • a formative tool installed thereon,
  • a mixing and dosing system, and
  • other components (pre-drying unit for the reinforcing fibers, monitoring of environmental conditions, etc.).

Furthermore, future expansion of data collection through additional system modules is considered (such as fully integrated non-destructive online quality assessment).

Building on the plant technology, Selfbits defines and implements the data interface and processing in the project. Large amounts of data are first checked for plausibility and pre-processed to reduce the bandwidth for transfer into a cloud database. After transfer to a data warehouse, the process data is analyzed and processed using statistical methods. The use of AI methods for data analysis is evaluated in the case of large data volumes. The results of data processing are returned to the production line in the form of recommendations via a web GUI. These assist the plant operator in quality assurance and optimization of process parameters.

Project Consortium

The Fraunhofer ICT has been investigating the reactive processing of ε-caprolactam since the early 2000s in several projects. The research institution brings extensive experience in coordinating national and international collaborative projects.

Selfbits GmbH is a spin-off of KIT (Karlsruhe Institute of Technology) that develops digital solutions in the field of Industry 4.0 and IIoT for medium-sized industrial companies. Thus, Selfbits brings comprehensive expertise in data acquisition, processing, and analysis to the project.

Bauer Systeme GmbH, as a medium-sized system provider with many years of experience in control engineering, measurement and control technology, as well as process engineering, brings the necessary expertise to realize a mixing and dosing system for in-situ pultrusion.

The Alfred Härer GmbH has over 50 years of expertise in the development, manufacturing, and repair of compression and injection molding tools. It can draw on extensive experience for the development and manufacturing of tooling technology for thermoset matrix systems.

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